1. Field of the Invention
The present invention relates generally to preservation of media (e.g., images, audio, video, documents, and the like) quality, and relates more particularly to restoring media quality in messaging environments.
2. Description of the Background Art
MMS (Multimedia Messaging Service) is a universally accepted standard that lets users of MMS supportive mobile phones send and receive messages with formatted text, graphics, photographs, audio, and video clips. Video sequences, audio clips, and high-quality images can be downloaded to the phone from WAP (Wireless Application Protocol) sites, transferred to the phone via an attached accessory (e.g., a digital camera), or received in an MMS message. MMS messages can be sent either to another MMS-enabled mobile phone or to an e-mail address. Photos, sound clips, and video clips can also be stored in the phone for later use. MMS supports standard image formats such as GIF and JPEG, video formats such as MPEG 4, and audio formats such as MP3 and MIDI. Multimedia messaging requires high transmission speeds, which can be provided by GPRS and 3G. To support the MMS technology, existing GSM or CMDA networks need an MMS-C (Multimedia Messaging Service Center).
These multimedia messaging environments provide a message generation service that allows a variety of message elements to be sent to a user. These message elements can contain text, animations, photographs, and sounds. In the future they may contain streaming audio and video. Users can compose their own messages, receive rich content messages from content providers, and forward them onto their own contacts. Examples include:                Taking a snapshot via a camera phone and sending to a friend        Composing your own animated picture messages and sending to friends        Sending audio files        Sending pictures & audio files with simultaneous playback        Receiving a picture postcard annotated with text and/or an audio clip        
Further, the user can also send messages from a variety of devices, including mobile phones, PDAs, Palm Pilots, or PCs. MMS makes it possible for mobile users to send these multimedia messages from MMS-enabled handsets to other mobile users and to e-mail users. It also makes it possible for mobile users to receive multimedia messages from other mobile users, e-mail users, and from multimedia-enabled applications.
In messaging systems like MMS, there is no central repository for storing media items or objects that are shared among subscribers. This is in contrast to many picture mail services, where a central switching server also stores the media objects (e.g., components in user-composed messages) centrally and persistently. In MMS, messages are instead created, and objects are sourced, at individual devices or terminals connected to the system without any central storage mechanism. Although a central switch in the form of a server may be employed to facilitate message delivery, the central switch or server does not attempt to operate as a central repository for storing or retaining media objects (unlike, say, picture mail services). MMS messages are composed using a standards-compliant messaging format and sent through a switch (e.g., MMSC for a MMS system) to one or more destinations (i.e., target devices or terminals). This is a “stored forward” approach, such that a given a message and its associated objects are stored on a temporary basis. Although the media objects may pass through one or more servers, any storage is at most transient in MMS systems; instead, the message and its media objects are stored just long enough to achieve delivery of the message. Once a given message has reached its target destination, the message's media objects will typically have been transcoded or otherwise decimated (e.g., convert media format, size, or the like), in an effort to optimize the rendering of the media objects for the target destination. Upon successful delivery of the message, the message itself and all of its associated media objects are discarded from temporary storage (e.g., at the central switch), or moved to off-line archival storage.
Given the simplicity of the MMS model where the central switch is only a transient switch, any high-quality media (e.g., audio, video, still images, etc.) that is destined for target devices that have less than full capability for rendering (e.g., less-capable display) will undergo quality degradation. In particular, the MMS-C switch will take the original high-quality media and create new lower-quality versions. Consider, for example, an original high-quality image. Here, the switch will often need to create a lower resolution image, in order to provide an appropriately-formatted image for the destination device. Apart from capability constraints of a given target device, bandwidth constraints may also mandate that media objects be converted into lower-quality copies (to conserve bandwidth). The destination device may use received media objects for composing other messages (e.g., forward or reply messages), but because of the foregoing degradation process the reused media objects become progressively poorer in quality. The scenario is similar to faxing and re-faxing a document. By the time the document has been faxed three or four times, the quality has degraded to the point where the fax copy is no longer usable. In the particular context of MMS, since there is no central repository for storing media objects, once a given media object has been degraded, the high quality of the original is not preserved because the association with the original media object has itself not been preserved. Overall, this leads to loss of quality and loss of flexibility for media items that are used in multimedia messaging systems.
In messaging systems of this type, as soon as the original media object (that is part of a message) is transcoded or otherwise converted for delivery to another mobile or terrestrial terminals, the original media quality is lost to the system (i.e., for subsequent use). To the point, the quality of delivered original media objects is forever lost for subsequent users as the system does not retain the quality in any way, shape, or form. Subsequent users of these delivered media items or objects (for new messages) are forever constrained to work with subsequent lower-quality versions.